The DofE award scheme is an excellent product, and well worth doing, but I would advise you to do it because you want to and not because you feel you have to - the same goes for any other extra-curricular activity. Some 'legacy' employers, such as BA, will give you credit for having done them (they see you as potential management, not just pilots), but in today's more mercenary employment climate, most airlines are only interested in your aviation qualifications.
Further maths, which also seems to be a common topic amongst you, is irrelevant to your aviation aspirations unless you wish to be an aeronautical engineering student at university - and we don't need you to be aeronautical engineering graduates in order to be pilots. O-level maths is as scientific as you need to get for the ATPLs, and for most employers.
Scroggs